Now, health and electrical lighting. Last month, Mariana Figueiro showed me something that she has developed to help seniors avoid falls in the night. Figueiro researches health applications at the Lighting Research Center at Rensselaer Polytechnic Institute in Troy, New York. Her project is a nightlight. But it's not just a single bulb. It's a string of yellow lights that border the darkened entrance to, say, a bathroom.

It's a doorway, and around the frame of the doorway are the yellow LEDs?

MARIANA FIGUEIRO: That's correct.

SIEGEL: Then they form - yeah, they form a nightlight.

FIGUEIRO: So there's two purposes here - or maybe three. One, it is a nightlight. Second, it tells you where the bathroom is, so it gives you where to go when you get up. And third, we did show that you increase stability with these kinds of light, compared to just night light.

SIEGEL: The geometric array of lighting, evidently, can help give us our bearings, and help us walk steadily in the dark. Elderly people in assisted living, she says, would be that much less likely to fall in the night en route to the bathroom.

Another of Dr. Figueiro's projects deals with the effect of lighting on Alzheimer's patients; specifically, on their sense of day and night, the internal body clock that we call the circadian system.

FIGUEIRO: What we're learning more and more is that the light that affects the circadian system is different than the light that affects the visual system.

SIEGEL: For example, we have long been accustomed to the yellowish, so-called warm light of incandescent light bulbs. Yellowish light helps us see things. But nothing says "wake up" to our circadian system like bluish light.

FIGUEIRO: The circadian system is what we call a blue sky detector. It's looking for blue light, when it comes to synchronizing the circadian system to solar day.

SIEGEL: And the theory is that our circadian system is looking for blue light because it's the blue of the blue sky?

FIGUEIRO: That is what people think.

SIEGEL: It turns out that bluish light is now commonly for sale at the hardware store. You can get it from compact fluorescents or from LEDs. It's often marketed as daylight. Mariana Figueiro has put that kind of light to use at the Albany County Nursing Home.

FIGUEIRO: Oh, that's my pretty table. That's my favorite.

DR. GUERMAN ERMOLENKO: This is our Alzheimer's unit...

SIEGEL: For patients with Alzheimer's, whose sleep cycle is off and who are too easily distracted to sit in front a bright lightbox, she has designed a lamp in the form of a table. The table top is a flat-screen TV that radiates a bright, bluish light. Figueiro has been working with Dr. Guerman Ermolenko, a geriatric psychiatrist.

ERMOLENKO: This is our famous table.

SIEGEL: Two elderly female patients were sitting at the table, staying awake - as they had been all day long - for weeks.

ERMOLENKO: Some of the residents who were sitting here used to wander a lot; used to be pretty irritable, especially during hands-on care when you need to change them. And now, we do see that they're pretty calm and happy.

SIEGEL: Karen Pitcher, the nurse manager in the Alzheimer's unit, says the two women at the table are sleeping through the night.

KAREN PITCHER: I've seen improvement. And the two people that spent the most time at the light table, had the most improvement.

SIEGEL: What is the improvement? What's improved?

PITCHER: They used to wander the halls at night. They used to get up multiple times during the night and be out in the hallway half-undressed, going from room to room. She doesn't try to exit the unit anymore. It's much better.

SIEGEL: The light table hasn't worked for all the Alzheimer's patients in the nursing home, as Dr. Ermolenko readily conceded.

ERMOLENKO: Some clients, it's too stimulating. And some clients, we had to actually cut it down and decrease the amount of light.

SIEGEL: But he says he's interested in expanding light therapy for the residents here and at another facility where he's already seeing good results, he says; not with a table, but with lamps in bedrooms.

For all the potential importance of lighting to people whose circadian rhythms are off kilter, the Alzheimer's unit at the Albany Nursing Home displays all the lighting design of, say, a 40-year-old middle school cafeteria. I asked Dr. Figueiro, the lighting researcher, about that.

Let me ask you your instinct here. I know this isn't science I'm asking you for. But we're in a room of - you know, a fairly large room full of people. And the lighting is, you know, medium to dim, I would say. And a lot of the bulbs are incandescent light bulbs in ceiling fixtures, a couple of fluorescent fixtures as well. If this space - let's say if half the lights were kind of bright, white, bluish light and if those were all on, you know, during the daytime and then it warmed up a little bit with yellowish light in the evening, do you think that would be a therapeutic environment?

FIGUEIRO: I think it would. And I think that ideally, what we want to do is to be able to replace the lighting, the entire lighting in the space because then everybody can get the benefit of having that kind of light. What I hope we can accomplish is show people that it works and be able to now translate that to architects, to people doing the building, so that when they design the building from start, they do it right.

SIEGEL: In fact, there are already LED bulbs on the market that change color, and that you can control with a smartphone or a tablet. They are very pricey. But they do raise interesting possibilities, and not just for Alzheimer's patients. If bluish light inspires wakefulness, it's probably not good lighting to read by at night, if you're hoping to fall asleep soon. The same goes for looking at the bluish glow of a laptop or a tablet. On the other hand, in the morning, a yellowish incandescent bulb may not provide the best light to help us seize the day.

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